This invention relates to a system for increasing the flow of liquid in a conduit such as a storm sewer system, and in particular relates to a system incorporating a series of barriers and air pumps which lift a portion of the liquid from the upstream side of each barrier to the downstream side.
Water resulting from rainfall or snowmelt or the like is usually removed from urban areas by means of an array of drainage conduits, often referred to as a storm sewer system. These conduits collect the water from the urban area serviced by that system and direct the flow through the system for discharge into a river, lake, reservoir or other suitable location. Urban development into new areas includes the construction of drainage conduits to service that new area. Those conduits often connect with existing storm sewer systems to transport water from those urban areas to the discharge location. This increases the volume of water flowing in existing systems and as development increases, waterflow volume will eventually exceed the capacity of the conduits in that system. This is particularly problematic during periods of heavy rainfall. It can also occur as a result of increased urbanization and the resultant increase in pavement and drainage gutters in those urban areas which link to existing drainage systems. The inability of existing systems to handle the increased water flow causes flooding in the drainage basin as water backs up. This flooding can result in damage to homes, vehicles and other objects within that flooded drainage basin which leaves municipalities with the problem of expanding existing storm sewer systems to adequately handle the increased flow of water in those systems.
One common method of increasing the capacity in rain water drainage conduits is to replace smaller capacity conduits with larger capacity conduits which are sufficient to handle the increased water flow. Another method of increasing the capacity of the entire drainage system is to provide additional conduits by "twinning" existing conduits to split the water flow among several conduits operating generally in parallel flow to accept the increased water flowing from the drainage basin. However increasing the flow capacity in these manners involves considerable capital expenditure and inconvenience caused by construction of these additional or increased capacity replacement conduits within an existing rain water drainage conduit system.
The need for an increased capacity rain water drainage system often occurs only during relatively short periods of time during heavy rainfall which results in flooding as the water accumulating in the drainage basin exceeds the flow capacity of the conduit system.
Accordingly there is a need for a conduit drainage system and method which increases the flow of liquid within an existing conduit system during periods of heavy water flow which flow would otherwise exceed the capacity of the conduit. Such a system would be activated only during periods of increased water flow, such as occurs during heavy rainfall exceeding the normal capacity of the conduit system.
There is further a need for such a system and method for increasing the flow of liquid within a conduit which is easily adapted to a variety of existing conduits of rain water drainage systems without requiring significant modification to the conduits and without interfering with the flow of liquid in the conduit during periods when flow within the conduit is within the normal capacity of the conduit.
Because these periods of increased water flow which exceed the capacity of existing conduits do not occur very often, the efficiency of the system in increasing the flow of water is less important as compared to the significant capital cost which would be required to replace or twin the existing conduit system with one of increased capacity to accept and transport an equivalent increased flow amount.
Air lift pumps are well known in the art and are used generally for lifting a liquid to higher level by using air pressure. The air is directed into a lower level of the pump where the liquid has accumulated. The air under pressure forces the liquid through the pump from the lower level to be discharged from the pump at a higher level. Air lift pumps operate on the principle that a mixture of air and water will rise in a pipe surrounded by water as the mixture of water and air in the pipe is lighter than the water outside the pipe.
While air lift pumps are considered to be relatively inefficient for lifting water as compared to submersible pumps, they do have advantages over these other types of pumps in that they do not have any moving parts and they take up very little cross sectional space within the conduit. The air compressor may be placed outside of the conduit with an air line providing the pumping energy into the water to pump it upwardly. These features permit easy retrofitting of an existing storm conduit system with a series of pumps to increase the flow capacity of liquid within that system with minimal construction cost. This also facilitating ongoing maintenance of the system by allowing maintenance of the compressor from outside the conduit system itself with minimal maintenance required within that system.